Determination of blood sedimentation is a routine procedure which has been widely applied for many years. In principle, blood sedimentation values are determined by taking a blood sample from a patient and mixing the blood with an anti-coagulant, normally a sodium citrate solution. The sample is then dispensed into a straight, vertically arranged pipette tube of standard internal diameter, in Sweden normally 2.5 mm, so as to obtain in the tube a column of blood of standard height, in Sweden normally 200 mm. The tube is then allowed to stand at a standardised temperature for a standardised length of time, during which the so-called sedimentation reaction takes place, during which reaction the red blood corpuscles form so-called coin rolls and settle to the lower part of the blood column, while the plasma collects above the sedimented blood corpuscles. When the aforesaid standardised time period has lapsed, the height of the plasma column is read-off and the reading obtained used as a measurement of the rate at which the blood settles, i.e. the so-called blood sedimentation rate.
Since the test used to determine the sedimentation of blood is a standard test widely used, methods and devices are sought for which enable blood samples to be taken and dispensed as quickly and as simply as possible. At present the actual sampling of the blood is normally effected in an extremely rational fashion, with the aid of a so-called vacuum blood sampling tube, (for example of the Venoject.RTM. or Vacutainer.RTM. kind). The open end of one such vacuum sample tube is closed by means of a rubber stopper and the interior of the tube is held under a partial vacuum and contains a given amount of an anti-coagulent, normally a sodium citrate solution. Such a vacuum sampling tube is used together with a sampling holder, which has the appearance of a plungerless injection syringe having inserted into its forward end a throughpassing, double-pointed disposable needle or cannula. The externally located point of the needle or cannula is inserted into the vein of a patient and the vacuum sampling tube then inserted into the cylindrical cavity of the holder, so that the rubber stopper located in said one end of the tube is pierced by the internal pointed end of the needle. Because of the partial vacuum prevailing in the vacuum sampling tube, blood will be drawn through the needle or cannula into the sampling tube. When sufficient blood has been drawn into the sampling tube, the tube is withdrawn from the holder, whereupon the hole formed in the rubber stopper when piercing the same is automatically sealed-off by the rubber as a result of its intrinsic elasticity. The needle of the sampling holder can be left in the patient's vein and further blood samples taken in a similar manner. The vacuum sampling tube containing the blood sample is shaken from side to side a number of times, either manually or in a special cradle designed for this purpose, so as to mix the blood with the anti-coagulent to the extent desired. This is a simple and quick method of taking blood samples and also eliminates practically completely all risks of blood, which may be contaminated, from being spilled or allowed to run free during the process.
Other kinds of sampling tubes are also available (for example tubes retailed under the trade name Monovette.RTM.). The only major difference between these tubes and those aforedescribed is that no partial vacuum is created within the tubes during their manufacture, but are instead provided with a manually displaceable plunger with which a partial vacuum can be created in the tube and blood drawn thereinto. In other respects the tubes function in the same manner as those beforedescribed.
In order to effect subsequent settling of the blood sample, it is necessary to dispense the mixture of blood and anti-coagulent from the sampling tube in which it is held to the aforesaid standardised pipette tube. In the methods normally applied hitherto (for example Sedipipette.RTM., Sedivac.RTM., and Sediplus.RTM.) it is necessary to remove the rubber stopper from the vacuum sampling tube and to dispense part of the blood sampled to the pipette tube in some manner, until a blood column of prescribed height is obtained therein. This is a relatively complicated labour-consuming and time-consuming task which requires particular expertise and familiarity on the part of personnel performing the task. Consequently, it is normal practice for private medical clinics and small medical centres to send blood samples to larger laboratories for analysis, instead of determining the sedimentation themselves. This practice, however, has serious disadvantages, since the waiting period between the time at which the blood sample is taken and the time at which the blood is dispensed has an indefinible effect on the sedimentation reaction and therewith on the measuring result itself. The sedimentation reaction, and thus the measuring result, is also deleteriously influenced by the shaking and vibrations to which the sample may be subjected during its transportation. The actual transfer of the sample from the vacuum sampling tube to the pipette tube, the so-called dispensing of the sample, also creates with these known methods a considerable risk of spilling some of the blood, which may be contaminated, such spillage being unavoidable in practice. Some of the sample will spill at the moment of withdrawing the stopper from the sampling tube, wherewith part of the sample unavoidably escapes to atmosphere in the form of an aerosol. Although methods and devices have been proposed with which the sampling tube and the pipette tube are coupled together in a manner which enables the sample to be dispensed from the sampling tube to the pipette tube with less risk of spillage, these methods and devices are complicated and relatively time and labour consuming, and also require the provision of additional apparatus.